Security is an important requirement in many printing applications. In situations such as official or government document printing, event ticket printing, financial instrument printing and the like, many printed materials must be protected against copying, forging and/or counterfeiting.
In some situations, document creators may wish to encode a security mark in a document in a way that is invisible to the human eye, but which becomes visible when the document is copied. For example, financial instruments such as checks, event admission tickets and other documents for which it is important to visually distinguish the original from a copy may include such security marks. An example of such a mark is a pantograph mark. The features of pantograph marks will be described below, but by way of example it is common to print a “void” pantograph mark on a document so that certain content of the security mark is not visible to the unaided human eye on the original, but the content will be visible on a copy of the original. An example of this is shown in FIG. 1, in which an original document 11, such as a bank check, has a security mark printed on it. The security mark includes the word “VOID”, but this word is not visible to the human eye in the original document 11. However, when a color copy 12 of the original document is printed, the word “VOID” is visible to the unaided human eye in the color copy 12.
The process of creating a pantograph mark that is suitable for a particular application can be a labor intensive process. Typically, several test marks are printed on test swatches using various patterns. The swatches are visually assessed, and the swatch that is determined to be best is used. The determination of “best” can be subjective, as it can consider how well the mark is hidden in the original and/or how prominent the mark appears in the copy. In addition, this process is time consuming, as it is common to print dozens, and in some cases hundreds, of test patterns to guide the process of selecting a pattern that is subjectively determined to be best.
This document describes methods and systems for creating a pantograph mark that addresses at least some of the problems described above, and/or other problems.